Nuclear was dead. After the Three Mile Island accident, people didn’t want reactors in their backyards. Bright young innovators were reluctant to study nuclear engineering, and an entire generation of technical expertise was lost. Nearly the whole environmental movement was firmly opposed to nuclear energy, and there was little political will for it elsewhere. Why incur political liabilities to build expensive nuclear plants when we could keep burning fossil fuels?

Then, there was a paradigm shift. People realized that the earth has been warming, and that the climate has been changing. A scientific consensus formed that carbon emissions were likely the chief culprit. When we burn fossil fuels (coal oil, and natural gas) for energy, they emit carbon dioxide. The current scientific consensus is that carbon dioxide and other “greenhouse gases” cause warming via absorption and emission of infrared radiation in the atmosphere. Although the share of man-made contribution to this remains a politically contentious issue, man’s responsibility for climate change has become a central tenant for the environmentalist movement, as well as much of the Democratic Party.

The ascendancy of climate change as a salient political issue was a major boon for nuclear energy.

Nuclear energy is the only source of electricity that is base load, scalable and carbon-free; the three main criteria necessary for a sustainable energy future. Base load energy supplies are those that remain constant in time. Solar energy, which oscillates daily with the sun, and wind energy, which vacillates intermittently with the breeze, cannot provide constant power supply. Tidal energy, like solar energy, is diurnal. Even biomass energy (produced from living or recently living biological material) is often seasonal. Fossil fuels such as coal, petroleum and natural gas are base load but not carbon-free—in fact, if the current consensus is correct, they exacerbate climate change. Many experts argue that biomass also shares this drawback.

Scalable energy sources can be “scaled up” or multiplied without restriction to meet any level of electricity demand. Hydroelectric and geothermal energy, although base load and nearly carbon-free, are not scalable. There are only so many suitable dam sites, and there are only so many suitable geologic “hot spots.” Thus, nuclear energy stands alone as a triune of sustainability: base load, scalable, and carbon-free.

Furthermore, nuclear energy is unique in that it is almost entirely geographically independent. The performance and viability of a wind or solar plant depends strongly on its location: wind doesn’t blow steadily everywhere, and the sun doesn’t shine brightly everywhere. Geography similarly severely restricts hydroelectric, geothermal, and tidal energy, as suitable sites are few and far between. Although we could build a fossil fuel plant anywhere, building it far from the actual fossil fuel resources would be imprudent, due to the costs and logistics of transporting large volumes of those fossil fuels over long distances. Consequently, we build most fossil fuel plants near natural deposits of fossil fuels.

In contrast, nuclear fuel is so small in volume that its transportation costs are negligible. There is no advantage to building nuclear plants near uranium mines. The only geographic constraint on nuclear plant sites is that they must be proximate to a body of water (such as a river, lake or ocean) for cooling purposes. However, even the absence of a natural body of water does not preclude a safe nuclear plant. For example, the Palo Verde Nuclear Generating Station operates in the Arizona desert by extracting water from a sewage treatment facility. Thus, nuclear energy is geographically independent in that its location does not affect its performance. It’s the same everywhere. It’s an excellent option for regions poor in natural resources. It’s flexible and adaptable.

Throughout the first decade of this century, nuclear energy began to resurge in the U.S. The 2005 Energy Policy Act authorized loan guarantees for potential new nuclear plants to help offset their large capital cost 1. As of 2011, two new reactors are under construction in Georgia, the first built in the U.S. in over 30 years. Two more will soon be underway in South Carolina. Enrollment in nuclear engineering university programs has dramatically increased, with over twice as many bachelor’s degrees awarded nationwide in 2009 than in 2002 2. In the 2008 presidential election, all five major candidates who received at least 10% of votes in their party primaries—Barack Obama, Hillary Clinton, John McCain, Mitt Romney and Mike Huckabee—at least tepidly supported more nuclear energy.

Around the world, 109 commercial reactors are either under construction or on order as of December 2010. These new reactors, mostly in Asia, will increase worldwide nuclear energy production by 28% 3. However, one of the most intriguing and surprising features of this “nuclear renaissance” has been entrepreneurial innovation in the startup community.

When Bill Gates stepped down as CEO of Microsoft in 2000, he had spent the last quarter of the 20th century transforming the world through personal computing. His stated goal was to spend the first quarter of the 21st century transforming the world through philanthropy. Through the Bill & Melinda Gates Foundation, he has developed strategies to eradicate poverty and improve health and education worldwide 4.

However, Gates’ philanthropic fervor is not limited to his foundation. He often independently partners with other members of Seattle’s ex-Microsoft coterie, especially Nathan Myhrvold, a prolific polymath who founded Microsoft Research 5. In his spare time, Myhrvold is a renowned paleontologist, an award-winning wildlife photographer whose work has appeared in National Geographic Traveler, and a master chef who has won the World Championship of Barbecue and published Modernist Cuisine, a vaunted tome on the science of contemporary cooking 6. He left Microsoft at about the same times as Gates to found Intellectual Ventures, a diverse innovation hub and patent licensing firm. Intellectual Ventures employs a wide range of scientists and engineers who invent and lawyers who patent. The aim of this organization is not only to patent new technology but also to facilitate its development and ultimate application 7.

Many of Intellectual Venture’s inventions originated from brainstorming sessions between Gates, Myhrvold, and their associate Lowell Wood, an astrophysicist who was involved with Ronald Reagan’s proposed “Star Wars” project. Wood conceived the mosquito laser, a device that that selectively and strategically zaps mosquitoes in order to combat malaria. This laser can discern the species and gender of an airborne insect and decide whether or not to zap it depending how it is programmed to manipulate the insect population. Intellectual Ventures is currently developing this Weapon of Mosquito Destruction (WMD) for future deployment in third world nations 8.

About six years ago, Gates, Myhrvold and Wood had another idea. They wanted to spur energy innovation for global sustainability. They surveyed all feasible energy sources, seeking one that is scalable, base load and carbon-free. Based on the same reasoning we employed earlier in this article, they identified nuclear energy as the most viable option. They brought in John Gilleland, a prominent nuclear fusion scientist, to lead the new initiative. Eventually, they founded a division within Intellectual Ventures called TerraPower, which later established itself as an independent startup company 9.

In order to improve waste management and use fuel more efficiently than conventional light water reactors, TerraPower opted to resurrect an older class of reactor—the “fast reactor”— with an innovative twist.

Nuclear reactors can be subdivided into two overarching classes: fast reactors and thermal reactors.

Thermal reactors are based on a paradox: While fission produces high-energy neutrons, low-energy neutrons can much more readily spur fission. Thermal reactors resolve this paradox by slowing or moderating the high-energy neutrons so that they become low-energy neutrons. They do this by introducing moderating materials, which contain light elements such as hydrogen or carbon. Water, heavy water and graphite are excellent moderators.

Fast reactors don’t bother resolving the paradox—they simply obviate it by enriching the content of heavy metal that is highly susceptible to fission. Since they must contain no moderating materials that would slow their neutrons, fast reactors must use exotic coolants consisting of heavier elements such as sodium, lead, or bismuth. They also offer a distinct set of advantages—more favorable thermal properties, less hazardous waste and the capability to breed more fuel to be used in other reactors. Sometimes, fast reactors can breed even more fuel than they burn.

In the 1950s, Admiral Rickover originally built two types of submarine reactors: first a thermal reactor cooled by light water (the USS Nautilus) and second a reactor cooled by sodium (the USS Seawolf). The Seawolf,—which Jimmy Carter would have helped command, had he not resigned his commission to return to a life of obscurity on his family peanut farm—sailed for two years on sodium. Unfortunately, due to some mechanical problems and concerns over the possibility of a sodium leak (sodium reacts violently with air and water), Rickover chose to discontinue the sodium program and focus on light water 10. The entire nuclear industry followed suit, and no one built sodium reactors in large numbers.

Although sodium fast reactors are an old concept, TerraPower opted to pursue an original, innovative type of sodium fast reactor known as the Traveling Wave Reactor (TWR). This propagates a “wave” through depleted uranium, a byproduct of uranium enrichment that is usually deemed unusable (it’s waste). This wave sustains itself by continuously breeding more fuel as it propagates. In the end, the TWR extracts much more energy from its uranium fuel than a light water reactor 11.

Furthermore, TerraPower’s TWR boasts superior safety features. The entire core is submerged in a large pool of sodium such that a loss of coolant accident (the scenario that caused the Three Mile Island incident) is exceptionally unlikely 12.

When I was twenty-four, I had the honor of helping out TerraPower. After completing my master’s degree, passing the doctoral qualifying exam, and knocking off the last of my required doctoral coursework, I opted to spend another gorgeous summer in the Pacific Northwest. I arrived in Bellevue, Washington on Memorial Day weekend. Bellevue is a familiar place for me—I was born there, and attended high school there. Originally a Seattle suburb, it has blossomed into a real upscale boom-burb with a flourishing downtown business center. Every time I return, there’s a new skyscraper. The place brings back memories.

When I was eighteen, I got a temporary job as a janitor on the construction site of Lincoln Center, now Bellevue’s central hub. I spent two months scraping up and sucking up dust and grime from subterranean labyrinths of newly constructed parking garages on the night shift. I quit that job when I left home for MIT. Now, whenever I return to Bellevue, I always park in one of those garages to enjoy a deep breath of dust-free air. I will always respect people who do that type of work, because it’s a lot harder than nuclear engineering.

TerraPower is about a mile south of downtown. It’s removed from the main Intellectual Ventures offices, the halls of which are populated with dinosaur replicas as per Nathan Myhrvold’s paleontological proclivities. There are about forty full-time employees, nearly all engineers. The work environment is strikingly different than what one might expect to find in the nuclear industry. The work pace is fast , as design features and goals can change on a weekly basis. Technical sessions are held with Gates and Myhrvold, who both have a surprisingly strong grasp of nuclear engineering, and often alter the design goals with a brilliant new idea or two. The engineers are young, something seldom seen in the nuclear industry. The attitudes are casual— afternoon breaks include team pushup sessions (a set of fifty is recommended). At TerraPower, an entirely new breed of millennial can be observed: the nuclear hipster.

I spent three months immersed in this unique and stimulating environment. My work centered on modeling the neutron physics of the core; mostly how to safely control and direct the fission chain reaction and power level. It was the most substantive and fulfilling work I have completed anywhere outside of academia. I continue to work closely with TerraPower on my doctoral thesis.

Seattle is an apt setting for the nuclear renaissance. Nestled between the pristine waters of Puget Sound and the serrated peaks of the Cascade Mountains, the beauty of nature is enveloping. The city is a bastion of progressive politics and the environmentalist movement. TerraPower’s presence there is emblematic of the new and unexpected alliance forged between nuclear engineers and environmentalists. The nuclear renaissance is about more than the resurgence of a technology – it’s about reconciliation. Scientific truth drove nuclear engineers and environmentalists, once adversaries, to become allies.

Mark Reed received his S.B. degree in Physics, as well as his S.B. and S.M. degrees in Nuclear Science and Engineering at the Massachusetts Institute of Technology (MIT), where he is currently pursuing a Ph.D. in Nuclear Science and Engineering. To view his previous pieces in Fortnight—including an exclusive video tour of the MIT Nuclear Reactor—see Violent Nascence, From War to Peace,Nuclear Waste & MedicineandNuclear Atrophy.